Optical element having an apodized aperture

ABSTRACT

Provided is an optical element with an electrochromic apodized aperture having variable light transmittance in response to the amplitude of an applied voltage. The apodized aperture includes (i) a first substrate having a planar inner surface and an outer surface, (ii) a second substrate having an outer surface and a non-planar inner surface opposing and spaced from the planar inner surface of the first substrate, wherein each of the planar inner surface of the first substrate and the non-planar inner surface of the second substrate has an at least partial layer of transparent conductive material thereover; and (iii) an electrochromic medium disposed between the planar inner surface of the first substrate and the non-planar inner surface of the second substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalPatent Application No. 61/119,393, filed Dec. 3, 2008, which isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to an optical element comprised of anelectrochromic apodized aperture having variable light transmittance inresponse to the magnitude of an applied electrical voltage.

BACKGROUND OF THE INVENTION

The makers of mobile communication devices such as cellular telephonescontinue to increase functionality of these devices. For example, atpresent cellular telephones can include still and video cameras, videostreaming and/or two-way video calling capabilities. Users can capturestill or video images and transmit the image or video files via anetwork. While the trend to increase functionality continues,manufacturers also continue to reduce the size of such communicationdevices.

The reduced size of such mobile communication devices have restrictedthe use of diaphragms with adjustable apertures or irises in the camerascontained therein. A mechanical camera iris is a diaphragm having avariable opening for a camera lens to alter the amount of light beingadmitted as well as to adjust the depth of field available for theimage. Such mechanical irises are utilized in most film cameras and inmany digital cameras. A mechanical iris is not practical for use inmobile communication devices because it would add too much bulk,increased costs, and may have unreliable performance. Thus,manufacturers typically do not include adjustable irises in cellulartelephones. The consequence is that cellular telephones neither producegood quality images at low light levels (due to, for example,objectionable shot noise and readout noise) nor at high light levelsdue, for example, to the inability to adequately decrease integrationtimes thereby creating over-saturation problems. Cellular telephonecameras also can exhibit poor depth of field and reduced image sharpnessdue to lens aberration.

SUMMARY OF THE INVENTION

The present invention is directed to an optical element comprising anelectrochromic apodized aperture having variable light transmittance inresponse to the magnitude of applied electrical voltage. The apodizedaperture comprises (i) a first substrate having an outer surface and aplanar inner surface, (ii) a second substrate having an outer surfaceand a non-planar inner surface opposing the planar inner surface of thefirst substrate, and (iii) an electrochromic medium disposed between theplanar inner surface of the first substrate and the non-planar surfaceof the second substrate. Each of the planar inner surface of the firstsubstrate and the non-planar inner surface of the second substrate hasan at least partial layer of conductive material thereover.

Also, the present invention is directed to an optical element comprisingan electrochromic apodized aperture having variable light transmittancein response to the magnitude of an applied electrical voltage. Theapodized aperture comprises (i) a first substrate having an outersurface and a planar inner surface, and (ii) a second substrate havingan outer surface and a convex inner surface opposing and spaced from theplanar inner surface of the first substrate to form a cavitytherebetween. Each of the planar inner surface and the convex innersurface has an at least partial layer of transparent conductive materialthereover; and (iii) an electrochromic medium disposed within thecavity.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Various non-limiting embodiments disclosed herein will be betterunderstood when read in conjunction with the drawings, in which:

FIG. 1 is a profile of an initial image of the aperture of the Exampleat time 0 determined as described herein;

FIG. 2 is a profile of an image of the aperture of the Example afterabout 1 second of applied voltage;

FIG. 3 is a profile of an image of the aperture of the Example afterabout 4 seconds of applied voltage;

FIG. 4 is a profile of an image of the aperture of the Example afterabout 18 seconds of applied voltage;

FIG. 5 is a profile of an image of the aperture of the Example afterabout 110 seconds of applied voltage;

FIG. 6 is a profile of an image with Gaussian curve fitting applied tothe Green line shown in FIG. 5;

FIG. 7 is a profile of the image resulting when no aperture was present;

FIG. 8 is a profile of the image resulting when the fixed aperture ofthe Comparative Example was present; and

FIG. 9 is a profile of an image with Gaussian curve fitting applied tothe Green line shown in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

As used in this specification and the appended claims, the articles “a”,“an”, and “the” include plural references unless expressly andunequivocally limited to one referent.

Additionally, for the purposes of this specification, unless otherwiseindicated, all numbers expressing quantities of ingredients, reactionconditions, and other properties or parameters used in the specificationare to be understood as being modified in all instances by the term“about.” Accordingly, unless otherwise indicated, it should beunderstood that the numerical parameters set forth in the followingspecification and attached claims are approximations. At the very least,and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, numerical parameters should beread in light of the number of reported significant digits and theapplication of ordinary rounding techniques.

All numerical ranges herein include all numerical values and ranges ofall numerical values within the recited ranges. Further, while thenumerical ranges and parameters setting forth the broad scope of theinvention are approximations as discussed herein, the numerical valuesset forth in the Examples section are reported as precisely as possible.It should be understood, however, that such numerical values inherentlycontain certain errors resulting from the measurement equipment and/ormeasuring technique.

The present disclosure describes several different features and aspectsof the invention with reference to various exemplary embodiments. It isunderstood, however, that the invention embraces numerous alternativeembodiments, which may be accomplished by combining any of the differentfeatures, aspects, and embodiments described herein in any combinationthat one of ordinary skill in the art would find useful.

As previously mentioned, the present invention provides an opticalelement comprising an electrochromic apodized aperture having variablelight transmittance in response to the magnitude of an appliedelectrical voltage. The apodized aperture comprises:

(I) a first substrate having an outer surface and a planar innersurface,

(ii) a second substrate having an outer surface and a non-planar innersurface opposing and spaced from the planar inner surface of the firstsubstrate, and

(iii) an electrochromic medium disposed between the planar inner surfaceof the first substrate and the non-planar surface of the secondsubstrate. Each of the planar inner surface of the first substrate andthe non-planar inner surface of the second substrate has an at leastpartial layer of conductive material thereover. The respectiverefractive indices of the second substrate, and the electrochromicmedium can be substantially the same. Also, the refractive index of thefirst substrate (i) is substantially the same as the respectiverefractive indices of the second substrate (ii) and the electrochromicmedium (iii). In the optical element of the present invention, a centerregion of the apodized aperture defines a “pupilary region” wherein theamount of the electrochromic medium is significantly less than thatpresent in the remainder of the apodized aperture. This serves tominimize (or eliminate altogether) coloration in this pupilary region.It has been found that the electrochromic aperture of the presentinvention offers several advantages over those previously known, and, inparticular, those where both of the opposing substrates are convex, orboth of the opposing substrates are concave. The electrochromic apodizedaperture of the present invention offers less complexity in design(e.g., alignment of the two inner surfaces of the opposing substrates isnot as critical) and thus less complexity in the manufacture of theapodized aperture.

The first substrate (I) and the second substrate (ii) can be comprisedof the same or different materials. For example, the first and secondsubstrates can comprise glass, such as fused silica or fused quartz, orpolymeric substrate materials. The first substrate (i) can compriseglass, and the second substrate can comprise a polymeric substratematerial or vice versa. Likewise, the first substrate (i) can compriseglass, and the second substrate (ii) can comprise glass. Alternatively,the first substrate (i) can comprise polymeric substrate material, andthe second substrate (ii) can comprise polymeric substrate material.

Suitable glass substrates can include but are not limited to any ofthose widely known (e.g., fused silica and fused quartz as previouslymentioned) and can include those having a refractive index of 1.40 orgreater, or 1.45 or greater, such as 1.50 or greater, or 1.65 orgreater. In a particular embodiment of the present invention, thesubstrate (i) and/or the substrate (ii) can comprise a glass having arefractive index of 1.40 to 1.75.

Suitable polymeric substrates can include without limitationpolycarbonate, polystyrene, polyurethane, polyurethane(urea), polyester,polyacrylate, polymethacrylate, poly(cyclic) olefin, polyepoxy,copolymers thereof, or mixtures of any of the foregoing. The polymericsubstrates can comprise a combination of any of the foregoingsubstrates, for example, in the form of a multilayer laminate. Thepolymeric substrates can be formed by any manufacturing means known inthe art such as by casting or molding, e.g., injection molding,techniques. In a particular embodiment of the present invention thepolymeric substrate comprises polycarbonates, poly(cyclic) olefins,polystyrenes, polyurethanes, polymethacrylates, co-polymers of any ofthe foregoing materials, or mixtures of any of the foregoing. Typically,both of the substrates (i) and (ii) are transparent (i.e., opticallyclear), however for some applications one or both may be tinted orotherwise colored. As used herein, by “transparent” is meant a substratethat has a luminous transmittance of at least 70 percent, such as atleast 80 percent, or at least 85 percent. Suitable polymeric substratescan include without limitation those having a refractive index rangingfrom 1.30 to 1.75, such as from 1.35 to 1.70.

As previously mentioned, the first substrate (i) has an outer surfaceand a planar inner surface, and the second substrate (ii) has an outersurface and a non-planar inner surface opposing the planar inner surfaceof the first substrate. The non-planar inner surface of the secondsubstrate (ii) typically is convex but may have a different non-planarsurface topography where desired, for example a spherical, parabolic, orhyperbolic topography. In a particular embodiment, the second substrate(ii) (which has a non-planar inner surface) can comprise a planarsubstrate having a partial-sphere or a half-sphere of the same ordifferent material affixed to the inner surface, thus forming a convexinner surface. Such a partial-sphere or a half-sphere configuration canbe formed, for example, by dispensing a UV-curable acrylic or epoxyresin material onto a planar surface of a glass or polymeric substrate.This configuration provides flexibility for refractive index matching ofthe substrates and the electrochromic medium disposed therebetween asdiscussed below.

Alternatively, the second substrate (ii) can be a unitary piece having aconvex inner surface comprised of any of the aforementioned substratematerials. In any event, the curvature of the convex inner surface ofthe second substrate (ii) is selected such that maximum apodization ofthe aperture is achieved.

At least one of the outer surface of the first substrate (i) and theouter surface of the second substrate (ii) can be substantially planar,that is, at least one of the respective outer surfaces can beessentially free of any wavefront distortion.

As aforementioned, each of the planar inner surfaces of the firstsubstrate (i) and the non-planar inner surface of the substrate (ii) hasan at least partial layer of transparent conductive material thereover.The conductive material can be selected from any of those widely knownin the field of electrochromic devices. For purposes of the presentinvention, the conductive material typically comprises a transparentconductive material selected from carbon nanotubes, gold, tin oxide,fluorine-doped tin oxide, indium tin oxide, and/or one or moreconductive polymers. Non-limiting examples of suitable conductivepolymers can include poly(acetylene), poly(pyrrole), poly(thiophene),poly(aniline), poly(fluorene), poly(pyridene), poly(indole),poly(carbazole), poly(azine), poly(quinone), poly(3-alkylthiophene),polytetrathiafulvalene, polynaphthalene, poly(p-phenylene sulfide),and/or poly(para-phenylene vinylene). For a detailed discussion ofsuitable conductive polymers, see Handbook of Conducting Polymers,2^(nd) ed., rev'd., Marcel Dekker, Inc., New York 1998. In the opticalelement of the present invention, the at least partial layer oftransparent conductive material on the respective inner surfaces of thefirst substrate (i) and the second substrate (ii) provides a surfaceconductivity ranging from 1 to 1000 ohm(s)/square, for example from 1 to500 ohm(s)/square, such as from 1 to 100 ohm(s)/square, or 3 to 80ohms/square, or from 5 to 50 ohms/square.

In a particular embodiment of the present invention, the at leastpartial layer of transparent conductive material on the non-planar innersurface of the second substrate (ii) opposes and is spaced from the atleast partial layer of transparent conductive material on the planarinner surface of the first substrate (i). The spacing distancetherebetween is dependent upon a number of factors, including but notlimited to the concentration of the electrochromic medium and thetopography of the inner surface of the second substrate (ii). Takinginto account such factors, the spacing distance is selected such thatthe coloration of the electrochromic medium within the pupilary regionof the apodized aperture is minimized or eliminated altogether. Thetransparent conductive material on at least one of the inner surface ofthe first substrate (i) and the inner surface of the second substrate(ii) can be electrically isolated in the pupilary region. By the term“electrically isolated” in the pupilary region is meant that thetransparent conductive material within the pupilary region on the innersurface of the first substrate (i) is isolated or insulated (e.g., asdescribed below) from electrical communication with the transparentconductive material of the second substrate (ii) or vice versa. Thispermits direct contact between (i.e., no spacing between the respectiveinner surfaces) the respective inner surfaces of the substrates (i) and(ii) without effecting a short circuit.

It is contemplated that one or both of the respective inner surfaces ofthe first substrate (i) and the second substrate (ii) can be essentiallyfree of the transparent conductive material in the pupilary region ofthe apodized aperture. This configuration provides an apodized aperturewherein there is no spacing between the first and second substrateswithin the pupilary region (without creating a short circuit) and thusthere is no coloration in the pupilary region. The apodized aperturewhich is essentially free of transparent conductive material in thepupilary region can be achieved by simply masking the pupilary region ofone or both of the respective inner surfaces of substrates (i) and/or(ii), then applying the transparent conductive material to the innersurface(s), and subsequently removing the mask to provide a pupilaryregion free of transparent conductive material.

Alternatively, the transparent conductive material in the pupilaryregion of one or both of the respective inner surfaces can be at leastpartially removed, for example, by laser ablation techniques. In oneembodiment, the transparent conductive material on a central portion ofthe pupilary region of the inner surface of the first substrate (i)and/or the inner surface of the second substrate (ii) can be isolatedfrom the remaining portion of the transparent conductive material onthat inner surface by removing a fine line of the conductive materialaround the central portion using laser ablation techniques (i.e.,creating an “island” of conductive material separated from the remainingconductive material layer on that inner surface). This permits directcontact of the respective inner surfaces of the two substrates (i.e., nospacing between the two) without creating a short circuit.

Likewise, the transparent conductive material on a central portion ofthe pupilary region of the inner surface of the first substrate (i)and/or the inner surface of the second substrate (ii) can be insulatedfrom the remaining portion of the transparent conductive material onthat inner surface by applying a non-conductive organic or inorganiccoating material (including any of those known in the art) onto thecentral portion of the pupilary region (i.e., creating an “island” ofnon-conductive material over the conductive material on that innersurface). This permits direct contact of the respective inner surfacesof the two substrates (i.e., no spacing between the two) withoutcreating a short circuit.

In a particular embodiment of the present invention, the non-planarinner surface of the second substrate (ii) is essentially free of thetransparent conductive material in the pupilary region. In thisalternative embodiment, the pupilary region of the inner surface of thesecond substrate (ii) which is essentially free of the transparentconductive material can be in direct contact with the transparentconductive material on the planar inner surface of the first substrate(i), provided that the conductive material which is present on the innersurface of the second substrate (ii) outside the pupilary region doesnot contact the conductive material on the inner surface of the firstsubstrate (i).

An electrochromic medium (iii) is disposed between the conductive layeron the planar inner surface of the first substrate (i) and theconductive layer on the non-planar inner surface of the second substrate(ii). The electrochromic medium (iii) can comprise any of theelectrochromic materials known in the art, and can be in any known form(for example, in the form of a liquid, a gel, or a polymeric material).For example, the electrochromic medium (iii) can be in the form ofsolvent-phase electrochromic medium. For purposes of the presentinvention, the terms “solvent-phase electrochromic medium” or“solution-phase electrochromic medium” are intended to includeelectrochromic media in the form of a liquid as well as a gel. In aparticular embodiment of the present invention, the electrochromicmedium comprises a solvent-phase electrochromic medium in the form of aliquid. The electrochromic medium includes at least one electrochromiccompound or dye, which varies in color or darkness in response to anapplied voltage. Typically, the electrochromic medium used in theoptical element of the present invention includes electroactive cathodicand anodic materials. In solution-phase electrochromic media, theelectrochromic compound(s)/dye(s) are contained in a solution in anionically conducting electrolyte. The material remains in solution whenelectrochemically reduced or oxidized.

Generally, the solvent-phase electrochromic medium contains at least oneanodic electroactive dye, at least one cathodic electroactive dye, and asmall amount of salt(s) that is/are soluble in a suitable solvent. Whena DC voltage is applied across the two respective transparent conductivelayers (typically separated by a low K material, e.g. a gasket or sealmember), the anodic dyes are electrochemically oxidized at the surfaceof the anode and the cathodic dyes are electrochemically reduced at thesurface of cathode. Color formation is accomplished when the molarextinction coefficient of the anodic dye and/or cathodic dye in thesolvent-phase electrochromic medium, change with their electrochemicalreactions. Generally, at least one of the dyes undergoes a significantincrease in extinction coefficient at a wavelength in the visible range.These colored species are free to diffuse from the electrodes (i.e., therespective transparent conductive layers) and meet each other in thebulk of the electrochromic medium. A redox reaction takes place betweenthe two electrochemically changed dyes to regenerate their respectiveoriginal states (i.e., the bleached or non-colored states). The finalcoloration of the apodized aperture is the result of an equilibriumbetween the electrochemical reaction at the electrode surfaces (i.e.,the respective surfaces of the transparent conductive layers) and adiffusion controlled redox reaction in the bulk of the solvent-phaseelectrochromic medium. In such a “self erasing cell”, a current at agiven applied voltage is required to maintain the apodized aperture inthe colored state. Without the applied voltage, the cell will eventuallyreturn to its original bleached state.

Notwithstanding the foregoing, the electrochromic coloration within theelectrochromic apodized aperture can be enhanced by applying aprogression of voltage pulses. The pulses can be applied either bypulsing voltage on and off, or by pulsing between two different appliedvoltages, and/or by pulsing to reverse polarity in order to reversecurrent flow direction. Coloration and de-coloration can be affected byadjusting (either individually or in any combination) the amplitude ofapplied voltage pulses (in either the positive or negative direction),the pulse time, and/or pulse frequency.

Also, it is contemplated that the apodized aperture can be structured toaccommodate the resistive heating of the apodized aperture, for example,through the use of a quick burst of battery power through one or both ofthe transparent conductive layers in plane (and not across theelectrochromic medium). Heating the aperture not only serves to increasethe kinetics of coloration of the electrochromic medium, but also toincrease the rate of fading back to the bleached state (“fade rate”).

The electrochromic medium employed in the optical element of the presentinvention can comprise any of the electrochromic compounds known in theart, including, for example, phenazine compounds, such asdihydro-phenazine compounds, and/or dipyridinium (i.e., viologen)compounds. Suitable non-limiting examples of such phenazine compoundsand the preparation thereof can include those described in U.S. Pat. No.6,020,987 at column 31, line 43, column 34, line 7, and in U.S. Pat. No.4,902,108 at column 13, line 49 to column 15, line 42, the citedportions of which are incorporated herein by reference. Suitablenon-limiting examples of viologen compounds include those described inU.S. Pat. No. 6,020,987 at column 34, line 8-55, incorporated herein byreference. See also, Electrochromism and Electrochromic Devices, Monk etal., Cambridge University Press 2007, Chapter 11, pp. 341-373,incorporated herein by reference in its entirety. Specific examples ofsuitable anodic electrochromic dyes can include but are not limited to5,10-dihydro-5,10-dimethylphenazene,N,N,N,N′-tetramethyl-1,4-phenylenediamine, 10-methylphenothiazine,10-ethylphenothiazine, tetrathiafulvalene, ferrocene and derivativesthereof, and/or triarylamines and derivatives thereof. Specific examplesof suitable cathodic electrochromic dyes can include but are not limitedto 1,1′-diphenyl-4,4′-bipyridinium difluoroborate,1,1′-di(n-heptyl)-4,4′ bipyridinium difluoroborate, 1,1′-dibenzyl-4,4′bipyridinium defluoroborate, and/or1,1′-di(n-propylphenyl)-4,4′-bipyridinium difluoroborate.

In addition, the electrochromic medium also may include other materialssuch as solvents (e.g., polar aprotic solvents), light absorbers, lightstabilizers, thermal stabilizers, antioxidants, thickeners or viscositymodifiers (e.g., polyvinylpyrrolidone), and free standing gel, includingpolymer matrices. The electrochromic medium can include a solventcomprising propylene carbonate, benzonitrile, phenoxyacetonitrile,diphenyl acetonitrile, sulfolane, sulfolate, and/or phosphoramide Otheruseful solvents can include, but are not limited to phosphoric esterssuch as tricresyl phosphate, cresyl phosphate and the like, amides suchas N,N-di-methylformamide, methylpropionamide, N-methylpyrrolidone,hexamethylphosphonamide, diethylformamide, tetramethylurea and the like,nitriles such as acetonitrile, sulfoxides such as dimethylsulfoxide,esters such as ethyl acetate, butyl acetate, dioctyl phthalate and thelike, carbonates such as propylene carbonate, ethylene carbonate and thelike, lactones such as .gamma.-butyrolactone, ketones such as methylethyl ketone, methyl isobutyl ketone and the like. Any of theaforementioned solvents maybe used singly or in any combination. Theviscosity of the solvent can influence the response speed of theelectrochromic coloration. Thus, when higher response speeds are needed,solvents of lower viscosity typically are used.

Additionally, the solution-phase electrochromic medium can comprise adissolved electrolyte, for example, tetrabutylammonium tetrafluoroborateand/or tetrabutylammonium bromide to provide ionic conductivity to thesolution. Electrolyte materials suitable for this purpose are well knownin the art.

As previously mentioned, in the optical element of the presentinvention, the refractive indices of the second substrate (ii), and theelectrochromic medium (iii) can be substantially the same. By“substantially the same” refractive index is meant that the differencebetween the respective refractive indices of each of the secondsubstrate (ii), and the electrochromic medium (iii) is not more than+/−0.005, for example not more than +/−0.004, or not more than +/−0.003,or not more than +/−0.002. Thus, the second substrate (ii) and thecomposition of the electrochromic medium (iii) are selected such thatthe respective refractive indices of (ii) and (iii) are substantiallythe same. Also, the respective refractive indices of the first substrate(i), the second substrate (ii), and the electrochromic medium (iii) canbe substantially the same. Such a “match” of refractive indices of (ii)and (iii), and where desired (i), provides an optical element havingexcellent optical qualities.

It should be noted that if the differences between the respectiverefractive indices of the substrate (ii) and the electrochromic medium(iii), and, where desired, the first substrate (i), are greater thanthose values stated above, for example, a difference of about +/−0.01,or a difference of about +/−0.1, the optics of the optical device inwhich the apodized aperture is employed, (e.g., a cellular telephonecamera) could be modified to adjust for this lack of refractive indexmatching. Simply put, in some instances it may not be desirable to“match” the refractive indices of (ii) and (iii), and where desired (i),as discussed above. In such instances, the optical power of the opticalelement can be maintained by adjusting the various components of theoptical element itself, and/or by adjusting one or more of thecomponents of the device in which the optical element is employed. Forexample, when the apodized aperture is used in a cellular telephonecamera, the apodized aperture can be used in conjunction with a cameralens having a particular power. Likewise, power can be introduced in oneor both of the substrates of the apodized aperture itself. The apodizedaperture itself may be used as a lens by balancing the respective shapesand refractive indices of the first and second substrates, as well as byadjusting the electrochromic medium.

In the optical element of the present invention, the electrochromicapodized aperture can further comprise at least one seal member (iv)about the outer perimeter of the apodized aperture and in contact withthe first substrate (i), the second substrate (ii), and theelectrochromic medium (iii) to protect and contain the electrochromicmedium between the transparent conductive layers on the respective innersurfaces of the first and second substrates. Such a seal member shouldbe comprised of a material having good adhesion to glass and/orpolymeric substrate materials, and to the conductive layers. Also, theseal member should exhibit low permeabilities for oxygen, moisture vaporand other gases, and should not interact with or contaminate theelectrochromic medium it is meant to contact and contain. Suitablematerials for use as the seal member include, but are not limited tothermoplastic, thermosetting and UV curing organic sealing resins suchas any of those known for use in liquid crystal devices. (See U.S. Pat.Nos. 4,297,401, 4,418,102, 4,695,490, 5,596,023, and 5,596,024.)Suitable materials for use as the perimeter seal member are low Kmaterials as mentioned above. Several non-limiting examples of suitableseal materials can include those based on epoxy, polyolefin (such aspolypropylene, polyethylene, copolymers and mixtures thereof),silicones, polyesters, polyamides and/or polyurethane resins. Any of theaforementioned materials can be silane-modified to enhance the bondingthereof to the substrate materials, e.g. glass. Suitable adhesives canbe used where appropriate to adhere the seal member to the substrates(i) and (ii).

Also, it should be noted that of one or more adhesives such as any ofthose known in the art, can constitute the seal number. Suitableadhesives for the purpose can include but are not limited to adhesivesbased on thermoplastic, thermosetting and UV curing organic resins.Suitable adhesives can include, for example, those based on epoxy,polyolefin (such as polypropylene, polyethylene, copolymers and mixturesthereof), silicones, polyesters, polyamides and/or polyurethane resins.The use of solder glass materials such as those described athttp://www.us.schott.com/epackaging/english/glass/technical_powder/solder.htmlis contemplated as well.

Obviously, any physical contact between the respective transparentconductive layers provided on the inner surface of the substrate (i) andon the inner surface of the substrate (ii) (which serve as electrodes)should be avoided in order to prevent shorting (i.e., a short circuit)during operation of the apodized aperture. Thus, in particularembodiments of the present invention, the respective transparentconductive layers should be spaced one from the other. Theaforementioned seal member itself can serve as a spacer, and/or separateoptical element members comprised of insulating materials can be used asspacers to maintain the physical separation of the respectivetransparent conductive layers.

As used herein, the term “apodized” and related terms (e.g., apodizing,apodization, etc.) refer to an aperture, which has a smooth and gradualtransition along its radius from the greatest percentage of transmittedlight (e.g., at the center of the aperture) to the lowest percentage oftransmitted light (e.g., at the edges of the aperture). A fully apodizedaperture would be one for which light transmittance (T) varies along itsradius (x) as a Gaussian curve (that is, T=exp(αx²). When employed as anoptical element, for example, as a camera iris, the electrochromicapodized aperture of the present invention emulates the pupil of thehuman eye in that it facilitates automatic “dilation” and“constriction”. As the excitation energy increases, the apertureconstricts so as to reduce the amount of light through the lens. Theconstricting aperture enabled by the present invention changes (i.e,increases) the effective f-number of the lens system and thereforeincreases its depth of field. Similarly, as the excitation energydecreases, the aperture dilates so as to increase the amount of lightthrough the lens. As the aperture becomes completely transparent thefull aperture is limited only by the lens mechanical stop (assuming noother system elements serve as limiting factors). Thus, the apodizedaperture is characterized by a Gaussian radial transmittance curve. Thethickness of the electrochromic medium increases along a radius of theapodized aperture and varies with the non-planar (e.g., convex) innersurface of the second substrate.

Generally, the at least partial layers of transparent conductivematerial on the inner surface of the first substrate (i) and the innersurface of the second substrate (ii) serve as counter-conductingelectrodes in electrical communication with a controller which isoperable to energize the electrochromic aperture by applying anelectrical voltage thereto. The magnitude of the electrical voltageapplied varies in response to light conditions as determined, forexample, by a photo sensor, such as the CMOS image sensor of a typicalcell phone camera module. As previously mentioned, the present inventionprovides an apodized aperture which “opens” to allow a greater amount oflight to pass through in low lighting conditions (i.e., where theelectrochromic medium is de-energized by reducing or removingapplication of voltage); and which “closes” to attenuate or block aportion of light when conditions are brighter (i.e., where theelectrochromic medium is energized by application of an appliedvoltage). The electrochromic medium thus provides an apodized aperturehaving a smooth and gradual transition along its radius from thegreatest percentage of transmitted light (e.g., at the center of theaperture in the pupilary region) to the lowest percentage of transmittedlight (e.g., at the edges of the aperture) in order to provide improvedresolution and overall focusing, for example by a lens and sensor. Theelectrochromic medium may be automatically energized and/or de-energizedand/or continuously varied in response to changes in the sensed lightingconditions surrounding the imaging array sensor, thereby providingimproved illumination of the sensor during low light conditions whilefurther providing improved focusing and greater control of lensaberrations during higher light conditions.

In a particular embodiment, the present invention is directed to anoptical element comprising an electrochromic apodized aperture havingvariable light transmittance in response to the magnitude of an appliedelectrical voltage, the apodized aperture comprising: (i) a firstsubstrate having an outer surface and a planar inner surface, and (ii) asecond substrate having an outer surface and a convex inner surfaceopposing and spaced from the planar inner surface of the first substrateto form a cavity therebetween, wherein each of the planar inner surfaceand the convex inner surface has an at least partial layer oftransparent conductive material thereover, the conductive materialcomprising, for example, indium tin oxide; and (iii) an electrochromicmedium disposed within the cavity. The refractive indices of the secondsubstrate, and the electrochromic medium can differ by not more than+/−0.003. In this embodiment, the electrochromic apodized aperturefurther can comprise a seal member (iv) comprised of any of theaforementioned seal member materials about the outer perimeter of theapodized aperture and in contact with the first substrate (i), thesecond substrate (ii), and the electrochromic medium (iii). A suitableadhesive can be used to affix the seal member to the substrates (i) and(ii), or the adhesive itself can serve as the seal member. Therefractive indices of (i), (ii) and (iii) can differ by not more than+/−0.003. Further, at least one of the outer surface of (i) and theouter surface of (ii) is substantially planar.

The electrochromic apodized aperture of the present invention usually isimplemented in conjunction with a pixilated imaging array sensor, suchas a CCD or CMOS chip. However, the electrochromic apodized aperture canbe implemented in conjunction with other types of sensors, and may beimplemented with or without a color filter or process associated withthe sensor, without affecting the scope of the present invention.

In any of the optical element(s) of the present invention the respectiveouter surfaces of the first and second substrates of the apodizedaperture can be at least partially coated with at least one coatingchosen from protective coatings, such as hard coats and/orabrasion-resistant coatings, anti-reflective (“AR”) coatings,antifogging coatings, oxygen barrier coatings and/or infra-red (IR)absorbing coatings and/or IR reflective coatings, and/or conventionalreflective coatings connected to at least a portion of the outer surfaceof one or both of the substrates Note that the coatings can, but neednot, cover an entire outer surface. Suitable non-limiting examples of ARcoatings can include a monolayer coating or multi-layer coating of metaloxides, metal fluorides, or other such materials, which may be depositedonto the outer surface(s) of the substrates (i) and/or (ii) or,alternatively onto self-supporting films that are applied to thesubstrate outer surface(s), through application means such as vacuumdeposition and sputtering techniques as are well known in the art.Suitable non-limiting examples of IR reflective coatings can includevery thin, partially transparent metallic layers such as NiCr and/or orgold layers applied, for example, by PVD metallization methods. Suchmaterials and application means are available from CreavacVakuumbeschechtung GmbH of Dresden, Germany. Suitable examples of IRreflective coatings (e.g., Laser Gold and Laser Black) also areavailable from Epner Technology, Inc. Also, suitable IR reflectivecoatings can include the silver-based coatings available under thetradename AgHT™, and the gold-based coating available under thetradename AuARE™, from CPFilms Inc. of Canoga Park, Calif. Suitablenon-limiting examples of IR absorbing coatings are coatings whichcomprise IR absorbing dye materials, for example, those which arephotochemically stable under ambient light conditions, and which absorblight within the near-IR region of the spectrum, for example,5,5′-dichloro-11-diphenylamino-3,3′-diethyl-10,12-ethylenethiatricarbocyanineperchlorate (which provides peak IR absorption at about 830 nm); 2,4di-3-guaiazulenyl-1,3-dihydroxycyclobutenediylium dihydroxide, bis(innersalt) (which provides peak IR absorption about 780 to about 800 nm); and1-butyl-2-[2-[3-[(1-butyl-6-chlorobenz[cd]indol-2(1H)-ylidiene)ethylidene]-2-chloro-5-methyl-1-cyclohexen-1-yl]ethenyl]-6-chlorobenz[cd]indoliumtetrafluoroborate (which provides peak IR blocking at about 900 to about1000 nm).

Transitional coatings may also be employed. As used herein the term“transitional coating” means a coating that aids in creating a gradientin properties between two coatings. For example, although not limitingherein, a transitional coating can aid in creating a gradient inhardness between a relatively hard coating and a relatively softcoating. Examples of transitional coatings include radiation-curedacrylate-based thin films.

Suitable examples of protective coatings can include, but are notlimited to, abrasion-resistant coatings comprising organo silanes,abrasion-resistant coatings comprising radiation-cured acrylate-basedthin films, abrasion-resistant coatings based on inorganic materialssuch as silica, titania and/or zirconia, organic abrasion-resistantcoatings of the type that are ultraviolet light curable, oxygenbarrier-coating, UV-shielding coatings, and combinations thereof. Forexample, the protective coating can comprise a first coating of aradiation-cured acrylate-based thin film and a second coating comprisingan organo-silane. Examples of commercial protective coatings productsinclude SILVUE® 124 and HI-GARD® coatings, available from SDC Coatings,Inc. and PPG Industries, Inc., respectively.

Various embodiments disclosed herein will now be illustrated in thefollowing examples.

Examples

Section 1 describes the preparation of the electrochromic solution andindex matching of the solution and lens. Section II describes thefabrication of the electrochromic iris. Section III describes themethods used to test the electrochromic iris of the present inventionand a fixed aperture Comparative Example. Section IV describes theimaging results for the Example and Comparative Example presented asFIGS. 1-9.

Section I—Preparation of Electrochromic Solutions

Part A—Preparation of n-Heptyl Viologen Tetrafluoroborate

Preparation of n-heptyl viologen tetrafluoroborate was carried out intwo steps. The following materials were purchased from Aldrich withoutpurification: n-heptyl bromide, 99% (629-04-9), 4,4′-bipyridine(553-26-4) 98%, acetonitrile (75-05-08), sodium tetrafluoroborate(13755-29-8) and tetrabutylammonium tetrafluoroborate (429-42-5).

Step 1 Preparation of Dibromides

To a 1,000 ml three necked round bottom flask was added acetonitrile(200 mL), 4,4′-dipyridine (0.08 mole, 12.5 g) and of n-heptyl bromide(0.25 mole, 45.23 g) and the solution was agitated by a mechanicalstirrer. The resulting clear yellow solution was heated to boiling overabout a 30 minute interval. After about 2 hours and 30 minutes, thesolution turned darker and yellow precipitates formed. The solution wasrefluxed at 80° C. for about 16 hours and afterwards was cooled to roomtemperature. The yellow precipitate was separated by filtration, washedwith fresh acetonitrile and air dried yielding 26.5 g of the product.The recovered product was used in Step 2 without further purification.

Step 2 Salt Exchange/Purification

Sodium tetrafluoroborate (0.22 moles, 24.15 g) was dissolved inapproximately 700 mL of deionized water in a one liter beaker withmixing and the product of Step 1 (0.045 mole, 23.1 g) was added. Theyellow product of Step 1 gradually changed color to white at ambienttemperature. After 2 hours of mixing, the white precipitate wasrecovered by filtration using a Büchner funnel with No. 54 filter paperto yield about 26 g of product. The recovered product was dried undervacuum in an oven at 90° C. for several hours yielding 21.4 g ofproduct. Analysis by an area % HPLC assay revealed it to be 99.9%. Theproduct (10 g) was recrystallized from 250 mL of deionized water in a600 mL beaker. The resulting suspension was heated and became clear whenthe temperature was about 90° C. The hot clear solution was filteredthrough No. 40 filter paper into two 300 mL Erlenmeyer flasks that wereheated on the same hot plate. The resulting filtrates were allowed tocool to ambient temperature and a crystalline precipitate formed. Therecrystallized product (6.8 g) was analyzed by an area % HPLC assaywhich indicated 100% without detectable impurities.

Part B—Preparation of Cell Solution

The following materials were obtained from Aldrich without purification:propylene carbonate (108-32-7), benzonitrile (100-47-0),5,10-dihydro-5,10-dimethylphenazine (DMPZ, 15546-75-5), andpolyvinylpyrrolidone (PVP,) with typical M, =1, 3 mM (9003-39-8).TINUVIN® P ultraviolet light absorber was obtained from Ciba Geigy.Refractive index at 589 nm/20° C. was measured through a digitalrefractometer from ATAGO, Automatic Digital Refractometer model RX-7000afollowing the manufacturers recommended procedures in the InstructionManual Cat. No. 3262.

Step 1 Preparation of Solvent Mixture

Benzonitrile (50.88 g) and propylene carbonate (49.12 g) were mixedtogether in a suitable container. The refractive index of the resultingmixture was 1.4816.

Step 2 Preparation of a 3% PVP Solvent Mixture

Polyvinylpyrrolidone (3 g) was dissolved into the product of Step 1(97.0 g). The refractive index of the resulting solution was 1.4819.

Step 3 Preparation of Stock Solution

Into a suitable container was added the product of Step 2 (20.0 g).Tetrabutylammonium tetrafluoroborate (0.10 M, 0.6585 g) and TINUVIN® Pultraviolet light absorber (0.0200 g) were added with mixing. Therefractive index of the resulting solution was 1.4821.

Step 4 Preparation of Electrochromic Cell Solution (0.06M)

n-Heptyl viologen tetrafluoroborate (0.1584 g) was dissolved into theproduct of Step 3 (5.0 g) resulting in a clear colorless solution. Tothe solution was added DMPZ (0.0631 g) and the color of the clearsolution became greenish. The refractive index of the resulting solutionwas 1.4844.

Part C—Index Matching of the Electrochromic Cell Solution to the N-FK5Hemispheric Lens

In order to match the refractive index of 1.4890 of N-FK5 glass (Schott)used for the electrochromic iris lens at a wavelength of 550 nm, it wasdetermined that the cell solution needed to match a refractive indexmeasured at 589 nm of 1.4851±0.0003, based on the optical dispersioncurve. The optical dispersion curve was determined using a MetriconPrism Coupler, Model 2010M and was calculated using the Cauchy fitmodule of the instrument operating software version 1.81.

The adjusting of the refractive index from 1.4844 to 1.4851 was carriedout by adding a 3 weight % PVP solution in 100% benzonitrile (0.0374 g)to the product of Step 4 (2.7550 g). The resulting solution was stirredwith about 0.5 g of 4A molecular sieve beads (8-12 mesh) for about 16hours and filtered through a 0.45 micron cartridge. The resultingrefractive index at 589 nm was 1.4850. Since the refractive indexobtained was within ±0.0003, no further adjusting was needed.

Section II—Fabrication of the Electrochromic Iris

The following materials were used: two Indium tin oxide coated glassslides measuring 25 mm by 25 mm by 1.1 mm, item X-178 from DeltaTechnologies; two 30 gauge needles; a hemispherical lens prepared from a2.5 mm ball lens of N-FK5 glass obtained from MSPT, Inc. Mountain View,Calif. that was ground down by Opticfab Corp. Santa Clara, Calif. untilresulting in a hemispherical lens having the curvature of the 2.5 mmball lens and a thickness of about 300 microns; Loctite® M-121HPT™Hysol® Medical Device Epoxy Adhesive; and DYMAX Light Weld® 429-gelglass adhesive;

Onto one of the ITO coated glass slide a rectangular space measuring 20by 25 mm was used to locate the components used to prepare the cell,This space was defined by one edge where a 30 gauge needle waspositioned at one top corner and another 30 gauge needle was positionedat 5 mm from the edge of the other top corner. The hemispherical lenswas placed in the center of the 20 by 25 mm rectangle. Another ITOcoated glass slide was placed over the rectangle so that a 5 mm edgefrom each of the ITO coated slides was exposed. The resulting assemblywas held together with miniature binder clips attached at the top andbottom of the assembly. The epoxy adhesive was used to fill the gap attwo opposite ends of the cell without touching the needles. The cell wasallowed to cure at ambient temperature overnight to fix the thickness ofthe cell and then the needles were removed. More epoxy adhesive was usedto fill the cell gap of all four sides except an approximately 0.2 mminlet at one edge. The cell was then cured at 105° C. for one hour tocomplete the process. Afterwards the cell was placed with the inlet downinto a beaker containing the index matched electrochromic cell solutionof Part C and placed into a vacuum chamber for 5 minutes at about 30inches of mercury. The vacuum was slowly replaced with nitrogen gas toenable the cell solution to be drawn up into the assembly. After thecell was vacuum filled with the product of Part C the opening was sealedwith the DYMAX Light Weld® 429-gel glass adhesive and cured by exposureto ultraviolet light in a DYMAX® 5000-EC chamber for 7 seconds. Theresulting cell was cleaned with acetone and both of the exposed ITOcoated surfaces were covered with copper conductive tape (about 6.3 mmwide) coated on the attached side with a conductive adhesive to serve asa busbar for easy electric connection. The resulting cell was exposed toultraviolet light in the DYMAX® 5000-EC chamber again for 7 seconds. Thebusbars of the cell were connected to a LAMBA Model LLS5018 powersupply. When the voltage was increased to greater to 0.6 V to 1.2 V thecell colored. When the voltage was decreased below 0.6 V the cell beganbleaching to the original colorless appearance.

Section III—Methods Used to Test the Electrochromic Iris

The product of Section II was placed in a mounting fixture about 40 to60 mm beneath the objective of an Olympus SZH10 zoom stereomicroscopebeing illuminated from the diffuse light source with maximum intensity.The microscope was set up using the 1.5× objective with the zoom settingset for 2.5. The aperture on the microscope was set to value 6. Themounting fixture was connected to a stage containing a manual plasticshutter.

In order to minimize the effects of room lighting, the eyepieces of themicroscope were covered with black plastic covers and black lightblocking material. Black plastic light blocking material was alsowrapped around the microscope stage area. The busbar areas of each sideof the electrochromic cell were attached to a LAMBDA LLS5008 digitalpower supply set to deliver 1.2 volts.

Images were acquired using an AVT Stingray 145C color digital cameramounted onto the microscope using a C-Mount connector. The digitalcamera was attached to a computer using a FireWire 800 cable andFirewire PCI card. Images were acquired using AVTs software (SmartView1.10). The camera was set up using the following settings: Format=F7Mode 0, ISO speed=400, Width=1388, Length=1038, Integration time=140milliseconds, high signal to noise ratio=8 images, frames persecond=0.85, and all auto-adjusting features, such as white balance,were turned off. Images were acquired for 300 images at a rate of 0.85frames per second. Of the 300 images, approximately 24 images wereacquired with the voltage to the sample being off, about 100 images withthe voltage on at 1.2 V, about 100 images with the voltage off and about75 dark images (manual shutter between the light source and the sampleclosed). The dark images were averaged and used to subtract out the darknoise from the camera system in the profiles shown below. The imageswere saved in RAW format.

The data was analyzed using Igor Pro (version 6.1×) from WaveMetrics,customized to auto analyze all the images acquired during the dataacquisition. The images were loaded into Igor Pro and converted from RAWformat to RGB format using a debayering function of RGRG . . . GBGB . .. as indicated in the AVT Stringray manual. Besides converting theimages from RAW to RGB, no additional image processing was performed onthe images analyzed and represented by FIGS. 1-9. The images for the “noaperture” in FIG. 7 and Comparative Example “fixed aperture” (300 micronprecision pinhole, mounted, from Edmund Optics, NT56-285) in FIGS. 8 and9 were collected using the same set-up except the integration time was120 milliseconds and the frames per second was 0.98. The intensityprofile extracted from each analyzed image was along a vertical linethrough the center of the image.

In addition to analyzing the images as a function of time, the softwarewas programmed to display a cross-sectional “intensity” profile of theiris as a function of time. Note that the profiles shown are from datawith the average dark image information subtracted out along the samecoordinates as the profile. The average dark image was an average of 60to 75 frames with the plastic shutter in the closed position (no lightpresent). Also note that the profiles were extracted from vertical rowsof the data and averaged over +/−8 pixels to improve the signal tonoise.

Section IV—Imaging Results

The intensity profiles for the electrochromic iris were derived fromimages taken for FIG. 1 at time 0, for FIG. 2 at about 1 second, forFIG. 3 at about 4 seconds, for FIG. 4 at about 18 seconds, and for FIG.5 at about 110 seconds. FIG. 6 shows the curve fitting of a Gaussiancurve onto the green response curve line of FIG. 5 after 110 seconds.FIG. 7 represents the profile with no aperture in place. FIG. 8represents the Comparative Example of a fixed 300 micron aperture. Theanalyzed images of the iris were collected via the SmartView 1.10software (with auto white balance applied before data acquisition andthen white balance was fixed) and displayed in Igor Pro. The intensityprofiles of the figures show the red, green and blue (solid curve, largedashes and small dashes, respectively) curves that were derived from thevertical rows of data on the images.

The profiles of FIGS. 1-6 demonstrate the function of an electrochromicapodized iris. When the voltage is off, the iris is full open in FIG. 1.When 1.2 V are applied, the electrochromic iris activates forming anapodized aperture as demonstrated after about 1 second in FIG. 2, afterabout 4 seconds in FIG. 3, after about 18 seconds in FIG. 4 and afterabout 110 seconds in FIG. 5. FIG. 6 demonstrates how closely the greenresponse (dashed curve) of FIG. 5 closely represents a Gaussiandistribution (solid curve), which is useful for apodization. TheGaussian width parameter obtained using Igor Pro's built in Gaussian fitroutines (with the resulting width parameter equal to Sqrt(2)*standarderror) was converted to a more traditional beam waist calculation forGaussian beams [2*standard error] by dividing the Igor Pro widthparameter by Sqrt(2) and multiplying that result by 2. The Gaussianwidth (beam waist) of the apodized aperture was about 316 microns. TheComparative Example “fixed aperture” profile (width about 300microns+/−10 microns) is shown in FIG. 8 and applied Gaussian curvefitting to the profile in FIG. 9. The profile in FIG. 9 clearlydemonstrates the difference between an apodized aperture (solid curve)and a fixed aperture (dashed curve). FIG. 7 demonstrates a profile withno aperture present.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. An optical element comprising an electrochromic apodized aperturehaving variable light transmittance in response to the magnitude of anapplied electrical voltage, the apodized aperture comprising (i) a firstsubstrate having a planar inner surface and an outer surface, whereinthe planar inner surface has an at least partial layer of transparentconductive material thereover; (ii) a second substrate having an outersurface and a non-planar inner surface opposing the planar inner surfaceof the first substrate, wherein the non-planar inner surface has an atleast partial layer of transparent conductive material thereover; and(iii) an electrochromic medium disposed between the planar inner surfaceof the first substrate and the non-planar inner surface of the secondsubstrate.
 2. The optical element of claim 1, wherein the refractiveindices of the second substrate, and the electrochromic medium aresubstantially the same.
 3. The optical element of claim 1, wherein therefractive index of the first substrate is substantially the same as therefractive indices of the second substrate and the electrochromicmedium.
 4. The optical element of claim 1, wherein at least one of theouter surface of the first substrate (i) and the outer surface of thesecond substrate (ii) is substantially planar.
 5. The optical element ofclaim 1, wherein the at least partial layer of transparent conductivematerial on the planar inner surface of the first substrate (i) and theat least partial layer of transparent conductive material on thenon-planar surface of the second substrate (ii) provides a surfaceconductivity ranging from 1 to 1000 ohms/square.
 6. The optical elementof claim 1, wherein the at least partial layer of transparent conductivematerial on the non-planar inner surface of the second substrate (ii)opposes and is spaced from the at least partial layer of transparentconductive material on the planar inner surface of the first substrate(i).
 7. The optical element of claim 1, wherein a center region of theelectrochromic apodized aperture defines a pupilary region.
 8. Theoptical element of claim 7, wherein the non-planar inner surface of thesecond substrate (ii) is essentially free of the transparent conductivematerial in the pupilary region.
 9. The optical element of claim 7,wherein the transparent conductive material on at least one of the innersurface of the first substrate (i) and the inner surface of the secondsubstrate (ii) is electrically isolated in the pupilary region.
 10. Theoptical element of claim 1, wherein the electrochromic medium comprisesa solvent-phase electrochromic medium.
 11. The optical element of claim10, wherein the solvent-phase electrochromic medium is in the form of aliquid.
 12. The optical element of claim 1, wherein the non-planar innersurface of the second substrate is convex.
 13. The optical element ofclaim 1, wherein the apodized aperture is characterized by a Gaussianradial transmittance curve.
 14. The optical element of claim 1, whereinthe thickness of the electrochromic medium increases along a radius ofthe apodized aperture.
 15. The optical element of claim 1, wherein thethickness of the electrochromic medium varies with the non-planar innersurface of the second substrate.
 16. The optical element of claim 1,wherein the conductive material comprises a transparent conductivematerial selected from carbon nanotubes, gold, tin oxide, fluorine-dopedtin oxide, and/or indium tin oxide.
 17. The optical element of claim 1,wherein the first substrate and the second substrate comprise the sameor different materials.
 18. The optical element of claim 17, wherein thefirst substrate and/or the second substrate comprises glass.
 19. Theoptical element of claim 18, wherein the first substrate and/or thesecond substrate comprises glass having a refractive index of 1.40 to1.75.
 20. The optical element of claim 17, wherein the first substrateand/or the second substrate comprises a polymeric substrate.
 21. Theoptical element of claim 20, wherein the first substrate and/or thesecond substrate comprises a polymeric substrate having a refractiveindex of 1.30 to 1.75.
 22. The optical element of claim 16, wherein thepolymeric substrate comprises polycarbonates, polyurethanes,poly(cyclic) olefins, polystyrenes, polymethacrylates, co-polymersthereof, or mixtures of any of the foregoing.
 23. The optical element ofclaim 1, wherein the first substrate (i) and the second substrate (ii)are transparent.
 24. The optical element of claim 1, wherein theelectrochromic medium comprises phenazine compounds and/or viologencompounds.
 25. The optical element of claim 1, wherein theelectrochromic medium comprises propylene carbonate, benzonitrile,and/or phenoxyacetonitrile.
 26. The optical element of claim 1, whereinthe electrochromic apodized aperture further comprises (iv) at least oneseal member about the outer perimeter of the apodized aperture and incontact with the first substrate (i), the second substrate (ii), and theelectrochromic medium (iii).
 27. The optical element of claim 1, whereinthe outer surface of the first substrate (i) and/or the outer surface ofthe second substrate (ii) is at least partially coated with at least onecoating chosen from protective coatings, antifogging coatings, oxygenbarrier coatings, antireflective coatings, IR absorbing coatings, IRreflective coatings, and/or conventional reflective coatings.
 28. Anoptical element comprising an electrochromic apodized aperture havingvariable light transmittance in response to the magnitude of an appliedvoltage, the apodized aperture comprising: (i) a first substrate havingan outer surface and a planar inner surface, and (ii) a second substratehaving an outer surface and a convex inner surface opposing and spacedfrom the planar inner surface of the first substrate to form a cavitytherebetween, wherein each of the planar inner surface and the convexinner surface has an at least partial layer of transparent conductivematerial thereover, the conductive material comprising indium tin oxide;and (iii) an electrochromic medium disposed within the cavity.
 29. Theoptical element of claim 28, wherein the refractive indices of thesecond substrate, and the electrochromic medium differ by not more than+/−0.003.
 30. The optical element of claim 28, wherein the refractiveindices of the first substrate (i), the second substrate (ii), and theelectrochromic medium (iii) differ by not more than +/−0.003.
 31. Theoptical element of claim 28, wherein at least one of the outer surfaceof the first substrate (i) and the outer surface of the second substrate(ii) is substantially planar.
 32. The optical element of claim 28,wherein the electrochromic apodized aperture further comprises (iv) atleast one seal member about the outer perimeter of the apodized apertureand in contact with the first substrate (i), the second substrate (ii),and the electrochromic medium (iii).